Heating apparatus for material subjected to super high pressure



March 23, 1965 A. ZElTLlN ETAL 3,175,068

HEATING APPARATUS FOR MATERIAL SUBJECTED T0 SUPER HIGH PRESSURE Filed Nov. 28, 1962 F/G. 2 4; 4/ H 0 2/ 401%) 44' 2/ 42 44 22:

INVENTORS. ALEXANDER ZEITLIN 8| JACOB BRAYMAN BY M,

their ATTORNEYS United States Patent 3,175,068 HEATING APPARATUS FOR MATERIAL SUB- JECTED T0 SUPER HIGH PRESSURE Alexander Zeitlin, White Plains, and Jacob Brayman, Staten Island, N.Y., assignors to Barogenics, Inc., New York, N.Y., a corporation of New York Filed Nov. 28, 1962, Ser. No. 240,691 9 Claims. (Cl. 219--50) This invention relates generally to pressure-responsive assemblies which are subjected to super high pressure by pressure-multiplying anvils or other pressure-exerting devices. More particularly, this invention relates to improvements in the provisions in such assemblies for heating material contained therein.

A pressure-responsive assembly of the sort described is typically comprised of an outer casing of pressuretransmissive material such as pyrophyllite, a body Within such casing of material to be subjected to high pressure, a heater sleeve surrounding such body and electrical connecting means by which opposite ends of the sleeve are connected to terminals on the exterior of the casing to permit current from an outside source to pass through the casing and sleeve to thereby produce electrothermal heating of the latter. In operation, the assembly is placed between two or more anvils, and the anvils are then actuated to compress the assembly while electric current is simultaneously passed through the sleeve to heat it and to thereby heat the body of material. In this manner, the material to be compressed is subjected at one and the same time both to high pressure and to high temperature.

In those prior art pressure-responsive assemblies, the heater sleeve has often been of a resistance too low to provide a good impedance match for power transfer purposes with a conventional source of voltage and current. Further, the transfer of heat from those sleeves to the body of material to be heated has been thermally ineficient because a large part of the heat of the sleeve has been emanated therefrom in a direction away from the said material. Still further, the previously used heating sleeves have been suscepticle to deformation and breakage during the compressing of the pressure-responsive assembly.

It is accordingly an object to this invention to provide a pressure-responsive assembly characterized by heating means which is free of one or more of the above-noted advantages.

Another object of the invention is to provide a heating means of the described sort which may be easily fabricated, and which is universally usable in a number of pressure-responsive assemblies of dilferent configurations.

These and other objects are realized according to the invention by providing in or for a pressure-responsive assembly an insulating core having a circumferential surface around which there extends a helical structure adapted to provide a path for heating or other current. By so using a helical shape for the path, the length of the path within the limited volume of the assembly may be increased to the extent where the end to end resistance of the path provides a good impedance match for power transfer purposes with a conventional current and voltage supply. Moreover, because the path extends around a central core which provide support therefor during compression of the assembly, the path is not as susceptible to deformation and breakage during compression as an unsupported, linear path, i.e., the path provided by a cylindrical heating sleeve, for example.

For a better understanding of the invention, reference is made to the following description of exemplary em- 3,175,368 Patented Mar. 23, 1955 bodiments thereof and to the accompanying drawings wherein:

FIGURE 1 is an isometric view of the one embodiment of the invention.

FIG. 2 is a fragmentary view which shows details of the helical structure in FIG. 1, and which is taken in cross section in a plane through the axis of the core element of FIG. 1;

FIG. 3 is a modification of the helical structure shown in FIG. 2; and

FIG. 4 is another modification of the helical structure shown in FIG. 2.

Referring now to FIG. 1, the reference numeral 10 designates a pressure-responsive assembly which is of cubic shape so as to be adapted for use in a cubic press (not shown) as, for example, the cubic press disclosed in US. Patent 2,968,837 issued on January 24, 1961, to Zeitlin et al. Such a cubic press has six pressure-multiplying anvils with identical square planar front faces somewhat smaller in size than the outside square faces of the assembly 10. Each of those six anvils is disposed opposite a respective one of the six faces of the assembly such that the front face of the anvil is centered on and bears against the adjacent assembly face. Because the front faces of the anvils are smaller than the assembly faces contacted thereby, the various anvils are separated from each other by inter-anvil gaps. In operation, the gaps between the anvils allow them to be moved inwardly to thereby compress the pressure-responsive assembly 10.

The mentioned assembly 10 is exteriorly comprised of a cubic casing 15 constituted of a pressure-transmissive material which may be pyrophyllite, and which is of the type ordinarly used for such casings, i.e., is a material characterized by high internal friction and by plasticity at high pressure. As shown, the casing 15 has a front end face 16, a rear end face 17 (of which only one edge is exposed in FIG. 1) and four more circumferential faces of which the faces 18 and 19 are exposed in FIG. 1.

The casing 15 has formed therein a cylindrical bore 20 extending through the casing from end face 16 to end face 17 in coaxial relation with the line of centers between those faces. Fitted within that bore is a matching cylindrical core 21 having a circumferential face 22 and, also, end faces 23 and 24 which are flush with, respectively, the end faces 16 and 17 of the casing. The core 21 is constituted of an insulating material (e.g., pyrophy-llite) which may be the same as or different from the material of the casing.

The circumferential face 22 of the core 21 has formed therein a helical groove 30 which progresses in the axial direction of the core from its end face 23 to its end face 24. Laid in the groove 30 is a helical structure 35 which provides a path for heating current, and which extends axially from a terminal 36 for such current at end face 23 to a similar current terminal (not shown) at the end face 24. The two mentioned current terminals may be provided by fabricating the helical structure 35 to have electroconductive end portions which are bent over to be received in separate shallow recesses formed in the end faces 23 and 24, respectively.

As shown by FIG. 2, the helical structure 35 may be a composite strip or laminarstructure in which the various component strips extend from side to side of the groove 30 formed in the core 21. The center one of the various superposed elements of structure 35 is a heater element or furnace 40, constituted of a strip or ribbon of stainless steel or other electrically resistant material which will not deteriorate when heated to a high temperature. That heater strip lies between two outer strips 41 and 42 which are constituted of a charge material to be heated and simultaneously compressed. The mentioned terminals of structure 35 may be provided by portions of strip 40 which project outwardly from the strips 41 and 42 at the opposite ends of the structure to form end tabs, and which are bent over as described.

To prevent short circuiting of the heater strip 40 by the charge strips 41 and 42 in the event the charge material of the latter is a good electrical conductor, current flow is prevented or limited between the strips 40 and 41 by an intermediately disposed insulating strip 43, and, likewise, current flow is prevented or limited between the strips 40 and 42 by an intermediately disposed insulating strip 44.

The insulating strips'43 and 44 may be constituted of resistive refractory material and may have a construction and electrical characteristics in accordance with the teachings concerning insulating sheaths of co-pending application Serial No. 120,820, filed May 10, 1961, in the name of Zeitlin and owned by the assignee of this application. A suitable insulation of the heater strip 40 from the charge strips 41 and 42 can on occasion be obtained by utilizing for the strips 43 and 44 an oxide coating formed on the opposite surfaces of the heater strip which face towards the charge strips.

The particular character of the material in the charge strips 41 and 42 is not critical to the invention. Thus, such material may be in the form in each of such strips of a loose powder or of a coherent mass. In the event the charge material is loose, such material may be held in place by an insulating sheath (not shown) surrounding the entire shown structure 35 and fitted into the groove 30 along with that structure.

In operation, the assembly is placed within the mentioned cubic press such that, as described, each of the six outside faces of the assembly is contacted by a respective one of the six anvils of the press. Of those six anvils, the two anvils which bear against end faces 16 and 17 make separate electric contacts with the two end terminals of heater strip 40 which are respectively disposed at one and the other of those two end faces. Those two anvils are utilized as conductors by which heating current is passed from an electric power supply through the heater strip 40 to thereby heat it to a high temperature. The heat from the heater strip is transmitted both radially outward (through the insulating strip 43) and radially inward (through the insulating layer 44) to thereby heat the charge material in each of the charge strips 41 and 42.

When the material in the charge strips has reached a desired temperature, the six anvils are simultaneously actuated to press inwardly on the assembly 10. In response to the pressure so applied, part of the pressure-transmissive material in the casing is extruded into the gaps between the anvils to there form gaskets which provide lateral support for the anvils, and which hold in the pressure generated in the main body of the casing. The remainder of the casing material becomes plastic to transmit in a hydrostatic manner to the charge strips 41 and 42 the pressure which is applied to the casing by the anvils. In this way, the material in the charge strips is simultaneously subjected both to high temperature and high pressure.

Because the heater strip 40 is helical rather than linear, its overall length is greatly elongated compared to the axial space within assembly 10 which the heater strip occupies. Since the resistance of strip 40 varies directly with its length, to so elongate the strip increases its resistance to facilitate the impedance matching thereof with a conventional power source so as, thereby, to provide for maximum power transfer from the source to the strip for the reasons explained in US. Patent 3,011,043, issued November 29, 1961, in the name of Zeitlin et al.

The principal directions of emanation of heat from strip 40 are radially inwards and radially outwards. Of the total heat generated by that strip, the inwardly emanated component serves to heat the charged material in strip 42, and the outwardly emanated component also serves to heat charge material, namely, that in strip 41. Since both of those components of heat from strip 41 are utilized to heat charge material and since a greater vollume of charge material is disposed nearer to strip than if that material were only one side of the strip, the heating of the charge material is characterized by greater thermal efiiciency than if all the charge material were disposed to receive heat from strip 40 in only one of its principal directions of heat emanation.

The performance of strip 46 as a heater element is aided by the strip construction thereof. Specifically, because the element is in the form of a thin strip or ribbon having two principal surfaces of heat emanation separated by only a small thickness of the material of which the element is constituted, the area of heat emanating surface of the strip is maximized relative to the cross sectional area thereof or, to put it alternatively, the cross sectional area of the strip is minimized for a given area of heatemanating surface provided per unit length by the strip. The strip construction of the heater element is thereby advantageous as compared to a heater element of solid circular cross section because to increase the area of heatemanating surface of the element is to increase its thermal efficiency as a heater (for the reason among others, that a greater volume of charge material may be located closer to the heater surface area of heat emanation), and to decrease the cross sectional area of the heater element serves to increase its resistance per unit length, the latter result being desirable for the heretofore mentioned purpose of matching the impedance of the strip to that of the power source.

As a further advantage of the construction shown in FIG. 1, it has been found that, during the compression of the assembly 16 by the anvils, the cylindrical core 21 provides for the helical structure 35 and inward support which greatly reduces the deformation of that structure (and the accompanying likelihood of interruption of current through the heater strip) as compared to that which occurs in the linear heater and charge structure characterizing the conventional pressure-responsive assembly. Thus, the shown construction greatly improves the reliability of operations wherein it is required both to subject the charge of a pressure-responsive assembly to high pressure and to maintain the heating of the charge over the period during which it is being compressed.

The core 21 and the helical structure 35 thereon together comprise a unit which can be fabricated separately from the pressure responsive assembly 10, and which can thereafter be incorporated into the assembly 10 by the simple operation of inserting the mentioned unit into the bore 29 formed in the casing 15 of the assembly. Because a bore suitable for receiving such a unit can be formed in pressure responsive assemblies having a wide variety of exterior geometric configurations, the mentioned unit 21, 35 is of universal application in the sense that it is readily employable in the described cubic assembly 10, in a tetrahedral pressure-responsive assembly (such as is disclosed in the mentioned US. Patent 2,968,837), in the cylindrical pressure-responsive assembly used with the well known belt apparatus, and so forth.

The helical structure 35 of FIG. 2 is shown in modified form in FIG. 3 asa structure 35 composed of elements 4t), 41, 42, 43' and 44 which extend radially outward from the bottom of groove 30, but which otherwise are similar in character to, respectively, the strips 41), 41, 42, 43 and 44 of the structure 35. As still another modification, the flat helical structure 35 of FIG. 2 may be replaced by the helical structure 35" of tubular cross section which is shown in FIG. 4, and which is comprised of the concentric elements of an inner heater'wire 4t)" of circular cross section, and outer cylindrical sheet 41" of charge material and an insulating sheath 42" interposed between the elements 40" and 41". Except for configuration, the elements 40", 41", and 42 are similar in character to, respectively, the elements 40, 41 and 42 of FIG. 2. If desired, the heater element 40" and the charge element 41" may be the outermost and innermost elements, respectively. Alternatively, the tubular structure 35" may have outermost and innermost elements of charge material, a heater tube disposed between those two charge elements, and two insulating sheaths of which each is disposed between the heater tube and a respective one of the two charge elements.

Because of the described correspondence between the elements of FIG. 3 and of FIG. 4 with those of FIG. 2, the details of the construction and operation of the FIG. 3 modification and of the FIG. 4 modification will be evident from the foregoing description of the construction and operation of the structure 35 of FIG. 2 and, accordingly, will not be described herein in detail.

The above-described embodiments being exemplary only, it will be understtod that additions thereto, omissions therefrom and modifications thereof can be made without departing from the spirit of the invention, and that the invention extends to embodiments differing in form and/ or detail from those specifically described. For example, if the charge material does not happen to be a good conductor of electric current the insulation between the heater element and the charge material may be omitted. Further, the described helical structure may be constituted of a single element corresponding to the described heater element in the instance where it is the material of that element which, specifically, is to carry current or is to be subjected to high pressure and/ or high temperature (e.g., the helical structure may be wholly constituted of bismuth wire Where it is desired to measure the resistance transitions of bismuth under increasing pressure of high magnitude). Evidently, two or more helical structures of the sort described may be placed in superposed relation in the helical groove 30 in core 21 or, alternatively, such two or more structures may be placed in separate helical grooves formed in the core. Instead of using only the single solid cylindrical core shown in FIG. 1, the pressure-responsive assembly may be moditied to incorporate a plurality of nested cylindricalcores of which each acts as a mandrel for one or more helical structures which are of the sort described, and which are received in one or more helical grooves formed in the circumferential surface of the core.

Accordingly, the invention is not to be considered as limited save as is consonant with the recitals of the following claims.

We claim:

1. A unit insertable into a bore formed in a pressurereceiving assembly adapted to be compressed by pressuremultiplying anvils, said unit comprising, a core of insulating material having axially spaced opposite end faces and a circumferential surface between said end faces, said circumferential surface having formed therein a helical groove extending around said surface and progressing axially from one to the other of said end faces, an elongated helical structure received in said groove and comprised of an elongated electrothermal heating element and of an elongated mass of charge material in superposed relation with said element to receive heat therefrom, said element being insulated from said mass of charge material, and said element providing a path for flow of electric current between the opposite ends of said structure, and a pair of current terminals for said structure, said terminals being flat-lying against said core at opposite ones of said end faces and being exposed at said end faces.

2. A unit according to claim 1 in which said helical structure is of circular cross section, and in which at least part of said charge material is disposed to have in a cross sectional plane normal to and through such element the form of an annular ring extending circumferentially around said heater element.

3. A unit according to claim 1 in which said heater element and mass of charge material are in the form of superposed strips to render said helical structure a composite strip structure.

4. A unit according to claim 3 in which said strips extend in said groove from side to side thereof.

5. A unit according to claim 3 in which said strips extend in said groove radially outwards of the bottom thereof.

6. A unit according to claim 3 in which said mass of charge material is divided into two strips disposed on opposite sides of the heater element strip.

7. A pressure receiving assembly adapted to be compressed by pressure-multiplying anvils, said assembly comprising, an outer casing of pressure-transmissive material, an insulating core member in said casing, an elongated structure extending helically around the circumference of said core member and progressing axially along said member, said structure being comprised at least in part of material to be subjected to pressure, and said structure providing a path for flow of electric current between the opposite ends thereof, and current terminal means exposed on the exterior of said assembly for connecting said opposite ends of said structure in circuit with a source of electric current.

8. A pressure-receiving assembly adapted to be compressed by pressure-multiplying anvils, said assembly comprising, an outer casing constituted of pressure transmissive material and having formed therein a bore extending through said casing between opposite sides thereof, an insulating core member fitted in said bore and having oppoiste end faces of which each is flush with a respective one of said opposite sides of said casing, an elongated structure extending helically around the circumference of said core member and progressing axially from one to the other of said end faces, said structure being comprised at least in part of material to be subjected to pressure, and said structure providing a path for flow of electric current between the opposite ends thereof, and a pair of current terminals for said structure at said opposite ends thereof, said terminals being flat lying against said core member at respective ones of said opposite end faces and being exposed at said end faces.

9. A pressure-receiving assembly adapted to be compressed by pressure-multiplying anvils, said assembly comprising, an outer casing constituted of pressure transmissive material and having formed therein a bore extending through said casing between opposite sides thereof, an insulating core member fitted said bore and having opposite end faces of which each is flush with a respective one of said opposite sides of said casing, an elongated structure extending helically around the circumference of said core member and progressing axially from one to the other of said end faces, said structure being comprised of an elongated electrothermal heater element and an elongated mass of charge material in superposed relation with said element to receive heat therefrom, and current terminal means exposed on the exterior of said assembly for connecting opposite ends of said heater element in circuit with a source of electric current.

References Cited by the Examiner UNITED STATES PATENTS 2,585,818 2/52 Moravec 219-50 3,011,043 11/61 Zeitlin et a1. 219-50 FOREIGN PATENTS 411,612 6/34 Great Britain.

RICHARD M. WOOD, Primary Examiner. 

1. A UNIT INSERTABLE INTO A BORE FORMED IN A PRESSURERECEIVING ASSEMBLY ADAPTED TO BE COMPRESSED BY PRESSUREMULTIPLYING ANVILS, SAID UNIT COMPRISING, A CORE OF INSULATING MATERIAL HAVING AXIALLY SPACED OPPOSITE END FACES AND A CIRCUMFERENTAIL SURFACE BETWEEN SAID END FACES, SAID CIRCUMFERENTIAL SURFACE HAVING FORMED THEREIN A HELICAL GROOVE EXTENDING AROUND SAID SURFACE AND PROGRESSING AXIALLY FROM ONE TO THE OTHER OF THE SAID END FACES, AN ELONGATED HELICAL STRUCTURE RECEIVED IN SAID GROOVE AND COMPRISED OF AN ELONGATED ELECTROTHERMAL HEATING ELEMENT AND OF AN ELONGATED MASS OF CHARGE MATERIAL IN SUPER- 